1. Field of the Invention
The present invention relates to a terminal connection structure used for, for example, conductively connecting a tail connection of wiring of a head suspension to a main flexible wiring board.
2. Description of the Related Art
A hard disk drive (HDD) has a hard disk and a magnetic head supported with a head suspension. The magnetic head is electrically connected through wiring of the head suspension to a main flexible wiring board on a main body of the HDD.
Between the wiring of the bead suspension and the main flexible wiring board on the main body of the HDD, a tail connection and a board side connection are formed for the wiring of the head suspension and the main flexible wiring board, respectively. The tail connection and the board side connection include terminals that are connected to each other by ultrasonic bonding, soldering, or adhering with the use of an anisotropic conductive film (ACF) as disclosed in JP10-256688A, JP2006-049751A, JP2007-173362A, JF2012-150872A, and JP2012-156371.
Recently, it is required for HDDs higher recording density and higher reliability. For this, additional functions may be incorporated into a magnetic head based on components such as a heater for controlling a flying height and a head disk interlace (HDI) sensor other than usual read/write elements. Further additional functions such as energy assisted recording are considered to be incorporated into the magnetic head. Accordingly, many magnetic heads have ten or more terminals including the terminals for the functions as well as the ground terminal.
According to the number of the terminals of the magnetic head, the number of wiring traces of the head suspension and terminals of the tail connection becomes ten or more. In a downsized HDD, the tail connection has a limit on the size thereof to inevitably involve downsizing and/or densification of the terminals. Many products, therefore, employ the connection with the use of the ACF in view of a risk of a short circuit and a workability as disclosed in JP 2012-150872.
FIGS. 11A to 12B illustrate terminal connection structures in which each one is applied to a tail portion of wiring of a head suspension to connect a tail connection 101 of the head suspension to a board side connection 103 of a main flexible wiring board on a main body of a HDD. FIGS. 11A and 12A are plan views partly illustrating the terminal connection structure with absence of the board side connection 103. FIG. 11B is a sectional view taken along a line XIB-XIB of FIG. 11A with the board side connection 103 represented with a chain double-dashed line. FIG. 12B is a sectional view taken along a line XIIB-XIIB of FIG. 12A with the board side connection 103 represented with a chain double-dashed line.
The tail connection 101 is configured that a wiring pattern 111 is laminated on a flat base insulating layer 107 and a cover insulating layer 109 covers the wiring pattern 111. A plurality of terminals 105 are arranged side by side at an end of the wiring pattern 111 to expose outside the cover insulating layer 109.
To the tail connection 101, the board side connection 103 is conductively connected through an ACF 113.
Around the terminals 105, parts of the cover insulating layer 109 are arranged on and protrude from surfaces of the terminals 105, respectively. The ACF 113 has a certain amount of flexibility and surely contacts with the surface of the terminals 105 if the number of the terminals 105 are relatively small as illustrated in FIGS. 11A and 11B. In this case, a sufficient degree of contact is secured between the surfaces of the terminal 105 and the ACF 113, and the protrusion of the cover insulating layer 109 has an insignificant effect on the electric connection.
If, however, the number of the terminals 105 are relatively large to cause the higher terminal density than the case of FIGS. 11A and 11B as illustrated in FIGS. 12A and 12B, the protrusion of the cover insulating layer 109 reduces the degree of contact between the surfaces of the terminals 105 and the ACF 113 and decreases the reliability of the electric connection.
In addition, such a problem is caused on a terminal connection for electronic devices other than the HDD for which the terminal connection structure connects between the tail connection 101 of the head suspension and the board connection 103 of the main flexible wiring board on the main body of the HDD.